Udo Nubbemeyer

Bio: Udo Nubbemeyer is an academic researcher from University of Mainz. The author has contributed to research in topics: Claisen rearrangement & Total synthesis. The author has an hindex of 17, co-authored 63 publications receiving 708 citations. Previous affiliations of Udo Nubbemeyer include Free University of Berlin.

Synthesis of Medium-Sized Ring Lactams

Abstract: Medium-sized ring lactams (7- to 15-membered) find widespread use in organic chemistry as key intermediates in the synthesis of more complex structures or as core structures in natural product or pharmaceutically important compounds. Until now, the generation of such rings is still a challenge in organic synthesis. During the past decade an increasing interest has focused on the generation of cyclic peptides as well as hairpin and β-turn mimics and the medium-sized rings were thought to represent suitable fragments. Furthermore, a range of complex natural products is characterized by such lactam structure and their total synthesis is a broad field for organic chemists to test new strategies and to develop new methods.

Diastereoselective Zwitterionic Aza-Claisen Rearrangement: The Synthesis of Bicyclic Tetrahydrofurans and a Total Synthesis of (+)-Dihydrocanadensolide.

Abstract: The zwitterionic Claisen rearrangement of optically-active N-allyl pyrrolidines and various acid chlorides proceeds with high simple diastereoselection (internal asymmetric induction) and high 1,2-asymmetric induction, generating a new C−C bond adjacent to a chiral C−O function. The resulting γ,δ-unsaturated amides were cyclized to the corresponding optically active γ-butyrolactones, which are useful intermediates in natural product synthesis. On one hand, a diastereoselective iodocyclization of several lactones led to tetrahydrofurans with a substitution pattern representing a key intermediate of an oxa-prostaglandin synthesis. On the other, a one-pot procedure of a Swern oxidation and consecutive Grignard reaction of one γ-lactone allowed a diastereoselective chain elongation. The final oxidation/cyclization sequence completed a highly efficient synthesis of the (+)-dihydrocanadensolide or its C-3 epimer, respectively.

Planar Chirality: Synthesis and Transannular Reactions of Unsaturated Optically Active Azoninones Bearing E-Olefins.

Abstract: The zwitterionic aza-Claisen rearrangement of optically active trans 4-silyloxy-2-vinylpyrrolidines and carboxylic acid fluoride generated nine-membered ring lactams with high yields. The reaction proceeded with an almost complete 1,4-chirality transfer and the exclusive generation of the E-double bond in the medium sized rings to cause additional planar chiral information. The initially formed azoninones were characterized by a pS-arrangement of the olefin with respect to the ring. The rather kinetically stable conformation underwent a flipping of the double bond to give the pR-azoninones as the thermodynamically stable products. The planar diastereomers were subjected to regio- and diastereoselective transannular ring contractions to give indolizidinones. The stereochemical outcome was strongly dependent from the planar chiral information of the double bond and the lactam unit. The so-formed optically active bicycles bearing a defined substitution pattern should serve as versatile building blocks in alkaloid synthesis.

Unusual Diastereoselection in the Synthesis of Nine-Membered Ring Lactams and Conformation-Controlled Transannular Reactions to Generate Optically Active Indolizidinones.

Abstract: The aza-Claisen rearrangement of vinylpyrrolidines 1 yielded almost exclusively the trans-3,8-disubstituted nine-membered ring lactams 2 (TBS=tBuMe2 Si), independent of whether cis or trans isomers were used as starting materials. The conformation (which provided facial chirality) of the medium-sized ring controlled the regio- and diastereoselectivities of the transannular reactions that afforded indolizidinones 3.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Recent developments in solvent-free multicomponent reactions: a perfect synergy for eco-compatible organic synthesis

Abstract: Multicomponent reactions have gained significant importance as a tool for the synthesis of a wide variety of useful compounds, including pharmaceuticals. In this context, the multiple component approach is especially appealing in view of the fact that products are formed in a single step, and the diversity can be readily achieved simply by varying the reacting components. The eco-friendly, solvent-free multicomponent approach opens up numerous possibilities for conducting rapid organic synthesis and functional group transformations more efficiently. Additionally, there are distinct advantages of these solvent-free protocols since they provide reduction or elimination of solvents thereby preventing pollution in organic synthesis “at source”. The chemo-, regio- or stereoselective synthesis of high-value chemical entities and parallel synthesis to generate a library of small molecules will add to the growth of multicomponent solvent-free reactions in the near future. In this review we summarized the results reported mainly within the last 10 years. It is quite clear from the growing number of emerging publications in this field that the possibility to utilize multicomponent technology allows reaction conditions to be accessed that are very valuable for organic synthesis. Therefore, diversity oriented synthesis (DOS) is rapidly becoming one of the paradigms in the process of modern drug discovery. This has spurred research in those fields of chemical investigation that lead to the rapid assembly of not only molecular diversity, but also molecular complexity. As a consequence multi-component as well as domino or related reactions are witnessing a new spring.

Chemogenetic Tools to Interrogate Brain Functions

Abstract: Elucidating the roles of neuronal cell types for physiology and behavior is essential for understanding brain functions. Perturbation of neuron electrical activity can be used to probe the causal relationship between neuronal cell types and behavior. New genetically encoded neuron perturbation tools have been developed for remotely controlling neuron function using small molecules that activate engineered receptors that can be targeted to cell types using genetic methods. Here we describe recent progress for approaches using genetically engineered receptors that selectively interact with small molecules. Called “chemogenetics,” receptors with diverse cellular functions have been developed that facilitate the selective pharmacological control over a diverse range of cell-signaling processes, including electrical activity, for molecularly defined cell types. These tools have revealed remarkably specific behavioral physiological influences for molecularly defined cell types that are often intermingled with p...